Blood bupivacaine concentrations after pecto-serratus and serratus anterior plane injections of plain and liposomal bupivacaine in robotically-assisted mitral valve surgery: Sub-study of a randomized trial

STUDY OBJECTIVE

To investigate the timing of peak blood concentrations and potential toxicity when using a combination of plain and liposomal bupivacaine for thoracic fascial plane blocks.

DESIGN

Pharmacokinetic analysis.

SETTING

Operating room.

PATIENTS

Eighteen adult patients undergoing robotically-assisted mitral valve surgery.

INTERVENTIONS

Ultrasound-guided pecto-serratus and serratus anterior plane blocks using a mixture of 0.5% bupivacaine HCl up to 2.5 mg/kg and liposomal bupivacaine up to 266 mg.

MEASUREMENTS

Arterial plasma bupivacaine concentration.

MAIN RESULTS

Samples from 13 participants were analyzed. There was substantial inter-patient variability in plasma concentrations. A geometric mean maximum bupivacaine concentration was 1492 ng/ml (range 660 to 4650 ng/ml) at median time of 30 min after injection. In 4/13 (31%) patients, plasma bupivacaine concentrations exceeded our predefined 2000 ng/ml toxic threshold. A second much smaller peak was observed about 32 h after the injection. No obvious signs of local anesthetic toxicity were observed.

CONCLUSIONS

Combined injection of plain and liposomal bupivacaine for pecto-serratus/serratus anterior plane blocks produced a biphasic pattern, with the highest arterial plasma concentrations observed within 30 min. Maximum concentrations exceeded the potential toxic threshold in nearly a third of patients, but without clinical evidence of toxicity. Clinicians should not assume that routine combinations of plain and liposomal bupivacaine for thoracic fascial plane blocks are inherently safe.

Absorption and pharmacokinetics of bupivacaine after bilateral topical administration in tonsillar fossae for posttonsillectomy pain relief

No previous studies have investigated the systemic absorption of bupivacaine when used topically for posttonsillectomy pain. The present study was undertaken to investigate the pharmacokinetics of bupivacaine after administration by a swab in the tonsillar fossae over 4 min after tonsillectomy. Eleven adult patients undergoing elective tonsillectomy were recruited. After removal of both tonsils, each of the two tonsillar fossae was covered with a swab moistened with 2 mL of bupivacaine 5 mg/mL, that is, a total of 20 mg bupivacaine. Blood samples were drawn after 0, 5, 10, 20, 30, 45, and 60 min. Bupivacaine was analyzed with an ultra-high-performance liquid chromatography-tandem mass spectrometry method. The highest single measured bupivacaine serum concentration was 23.2 ng/mL and took place 10 min after drug administration. Mean (±SD) Cmax was 11.4 ± 6.0 ng/mL and mean tmax was 11.3 ± 4.7 min. Mean t1/2 was 31.6 ± 9.3 min. As the toxic concentration threshold has been reported to be in the interval 1500-4500 ng/mL, the concentrations measured were well below 2% of the lowest cited toxic threshold. In conclusion, this study shows that applying 4 mL of bupivacaine 5 mg/mL by a swab in the tonsillar fossae posttonsillectomy yields very low plasma concentrations, suggesting its safe application without any risk of systemic toxic effects.

Assessment of Total Ropivacaine Concentration in Blood after Bilateral Pecto-Intercostal Fascial Block Combined with Rectus Sheath Block in Cardiac Surgery Patients

OBJECTIVES

Pecto-intercostal fascial block (PIFB) and rectus sheath block (RSB) have been combined to offer better analgesia for cardiac surgery patients, but safety of the analgesic protocol with a large volume of ropivacaine is uncertain.

METHODS

This is a prospective observational study at Peking University People's Hospital to investigate the pharmacokinetic profile of ropivacaine after combined regional blocks. Patients undergoing elective cardiac surgery by a median sternotomy were enrolled to receive bilateral PIFB and RSB with 70 mL 0.3% ropivacaine (total dose 210 mg). Blood was sampled at 5, 10, 15, 30, 60, 90 and 120 mins after blocks. Total blood concentration of ropivacaine for patients were measured.

RESULTS

Ten patients were enrolled and analyzed. The peak total ropivacaine concentration varied from 0.67 to 2.42 µg/mL. Time to reach the peak values mainly located between 10 and 30 mins after the performance. No patients had ropivacaine concentration values above toxic threshold (4.3 µg/mL), and there were no systemic toxicity symptoms during the perioperative period.

CONCLUSIONS

PIFB combined with RSB in a general injection of 70 mL 0.3% ropivacaine does not give rise to toxic levels, and it is an effective and safe analgesic protocol for cardiac surgery patients.

Micro-pharmacokinetics of lidocaine and bupivacaine transfer across a myelinated nerve fiber

BACKGROUND

The aim of the present study was to predict the time to onset and duration of action of two local anesthetics (lidocaine and bupivacaine) based on experimental dimensions of a typical nerve and experimental octanol/water partition coefficients.

METHODS

We began our compilation of experimental data with a numerical solution of the Smoluchowski equation for the transfer of lidocaine and bupivacaine across the axon membrane in the region of the node of Ranvier (axolemma) and across the Schwann cell. The difference between the aqueous and lipid environments of the neuron was simulated by including the coordinate-dependent chemical potential. In the second step, the permeation rates calculated using the diffusion equation were used to solve a system of four ordinary differential equations. This approach allowed us to simulate the cellular environment for a longer time and to compare our model with pharmacokinetic properties (time to onset and duration of action) of local anesthetics from the literature. The behavior of local anesthetics under physiological conditions and in case of local acidosis was also simulated.

RESULTS

We demonstrated that local anesthetics cross the axolemma in a time span of less than 1 μs. The time to onset of action, controlled by diffusion from the epineurium to an axon with a typical distance of 500 μm, was 167 s and 186 s for lidocaine and bupivacaine, respectively. The calculated half-life, which is a measure of the duration of action, was 41 min and 328 min for lidocaine and bupivacaine, respectively.

CONCLUSIONS

Duration of action is controlled by the storage capacity of lipophilic compartments around the axon, which is higher for bupivacaine but lower in local acidosis. For the latter case, the literature, including textbooks, provides a misinterpretation, namely that protonated species cannot penetrate the membrane.

Plasma concentrations of levobupivacaine in neonates during caudal epidural analgesia maintained over 48 hours

BACKGROUND

Differences in neonatal pharmacokinetics are known to cause systemic accumulation of levobupivacaine with adverse effects during epidural analgesia. Therefore, it is not recommended to surpass 48 hours of administration in neonates. Free and total levobupivacaine levels are considered as predictors of toxicity.

OBJECTIVE

The aim of the LEVON pilot study was to detect the accumulation of levobupivacaine during epidural analgesia exceeding 48 hours in neonates.

METHODS

Ten neonates received a loading dose of levobupivacaine (1.25 mg/kg) followed by a continuous infusion (0.2 mg/kg/hour) epidurally. Free and total levobupivacaine concentrations were measured 0.5, 1, 6, 12, 36, 72 and 144 hours after the start of infusion. Cumulative doses of levobupivacaine, pain scores and clinical signs of toxicity were used for assessing efficacy and safety.

RESULTS

The median concentrations of total levobupivacaine were 586.0, 563.0, 837.5, 957.0, 1930.0, 708.5 and 357.5 ng/ml. The median concentrations of free levobupivacaine were 4.0, 3.6, 5.5, 3.6, 5.5, 0.8 and 0.0 ng/ml. Three patients reached concerning concentrations of total levobupivacaine. Levels of free levobupivacaine remained low. No signs of toxicity were observed.

CONCLUSION

Caudal epidural analgesia with levobupivacaine lasting longer than 48 hours appears to be safe providing that free levobupivacaine levels are below the presumed threshold for toxicity (Tab. 1, Fig. 1, Ref. 29). Text in PDF www.elis.sk Keywords: free levobupivacaine, total levobupivacaine, neonate, caudal continuous epidural analgesia, postoperative pain.

Novel insights on the encapsulation mechanism of PLGA terminal groups on ropivacaine

Currently, the influences of free terminal groups (hydroxyl, carboxyl and ester) of PLGA on encapsulating active pharmaceutical ingredient are relatively ambiguous even though PLGA types were defined as critical quality attributes in vast majority of design of experiment process. In this study, emulsion method combined with premix membrane emulsification technique has been used to encapsulate ropivacaine (RVC), a small molecule local anesthetic in clinical. Based on the narrow particle size distribution, the influences and mechanisms of the terminal groups on properties of ropivacaine loaded microspheres have been investigated in detail. It was found that microspheres prepared by PLGA with hydroxyl or ester groups exhibited lower encapsulation efficiency but faster in vitro release rate than that of carboxyl groups. In the meanwhile, on microcosmic level analysis by quartz crystal microbalance with dissipation, atomic force microscope and confocal laser scanning microscopy, we attributed this distinction to the specific interaction between ropivacaine and different terminal groups. Subsequently, the reaction activation centers were verified by density functional simulation calculation and frontier molecular orbital theory at molecular level. Additionally, pharmacokinetics and pharmacodynamic research of infiltration anesthesia model were performed to compare sustained release ability, duration and intensity of the anesthetic effect in vivo. Finally, potential safety and toxicity were evaluated by the biochemical analysis. This study not only provides a novel mechanism of drug encapsulation process but also potential flexible selections in terms of various anesthesia indications in clinical.

Design, optimization and evaluation of co-surfactant free microemulsion-based hydrogel with low surfactant for enhanced transdermal delivery of lidocaine

Microemulsion is the preferred vehicle for local anesthetics; however, the toxicity and irritation associated with a quantity use of surfactants (S) and co-surfactants (CS), i.e., medium- or short-chain alcohols, restrict its commercial application. In this study, efforts have been made to enlarge the CS-free microemulsion area by mixing olive oil (OL) with α-linolenic acid (ALA) and linoleic acid (LA), and by using vitamin E succinate (VES) as an auxiliary oil. Through Box-Behnken design and the optimization of nondominated sorting genetic algorithm II, the optimal microemulsion formulation (M_E0) with a large steady-state simultaneous permeation rate (J_s) and skin retention was screened as 3.23% OL, 0.45% ALA, 1.81% LA, 0.91% VES, 13.60% S, 5% lidocaine and water. Three percent ethanol was screened as a permeability enhancer for the hydrogel of M_E0, which showed a statistical increase in J_s and skin retention through the abdominal skin of guinea pigs. The optimized formulation had desirable characterization, good stability and negligible irritation. The large J_s and skin retention were well reflected in the pinprick test, wherein intensity of anesthetic effect and duration of action were increased significantly over the commercial cream. The developed CS-free microemulsion hydrogel with low S could be a promising strategy for the topical delivery of lidocaine.

A review of the mechanism of the central analgesic effect of lidocaine

Lidocaine, as the only local anesthetic approved for intravenous administration in the clinic, can relieve neuropathic pain, hyperalgesia, and complex regional pain syndrome. Intravenous injection of lidocaine during surgery is considered as an effective strategy to control postoperative pain, but the mechanism of its analgesic effect has not been fully elucidated. This paper intends to review recent studies on the mechanism of the analgesic effect of lidocaine. To the end, we conducted an electronic search of the PubMed database. The search period was from 5 years before June 2019. Lidocaine was used as the search term. A total of 659 documents were obtained, we included 17 articles. These articles combined with the 34 articles found by hand searching made up the 51 articles that were ultimately included. We reviewed the analgesic mechanism of lidocaine in the central nervous system.

Transversus Abdominal Plane Block in Children: Efficacy and Safety: A Randomized Clinical Study and Pharmacokinetic Profile

BACKGROUND

The transversus abdominis plane (TAP) block has become a common regional anesthesia technique for pain management in a wide variety of abdominal procedures. Evidence to support any particular local anesthetic regimen as well as pharmacokinetic and systemic toxicity risks of TAP block remain insufficiently studied in children. The aim of this study was to compare the analgesic effects and investigate pharmacokinetic profile of levobupivacaine after ultrasound-guided TAP block using a low volume/high concentration (LVHC) or a high volume/low concentration (HVLC) solution in children.

METHODS

This prospective randomized study included children scheduled for day-case inguinal surgery. Children were randomized to receive TAP block using 0.4 mg·kg levobupivacaine as either HVLC (0.2 mL·kg of 0.2% levobupivacaine) or LVHC (0.1 mL·kg of 0.4% levobupivacaine). The primary outcome was the number of children who required opioid rescue analgesia postoperatively. Pharmacokinetic profile study of levobupivacaine was also performed.

RESULTS

Seventy patients were equally randomized, and 65 were included in the final analysis. Seventy-one percent of patients did not require any postoperative opioid analgesia. The number of patients who received rescue analgesia was 12 (35%) in the LVHC group and 7 (23%) in the HVLC group (relative risk, 0.64; 95% confidence interval [CI], 0.29-1.42; P = .26). Mean pain scores (FLACC [faces, legs, activity, cry, and consolability]) at postanesthesia care unit discharge did not differ between LVHC and HVLC groups, respectively, 0.39 ± 0.86 and 1 ± 1.71 with mean group difference -0.60 (95% CI, -1.27 to 0.06; P = .08). The pharmacokinetic profile of levobupivacaine was comparable in the 2 groups: the mean total and free levobupivacaine peak concentrations were 379 ± 248 and 3.95 ± 3.16 ng·mL, respectively, occurring 22.5 ± 11 minutes after injection. The highest total and free levobupivacaine concentrations collected, respectively, 1360 and 15.1 ng·mL, remained far below theoretical toxic thresholds.

CONCLUSIONS

In children, quality of postoperative pain control provided by TAP block using levobupivacaine 0.4 mg·kg administered as either HVLC or LVHC did not differ and was associated with a very low risk of local anesthetic systemic toxicity.

Interspace between Popliteal Artery and posterior Capsule of the Knee (IPACK) Injectate Spread: A Cadaver Study

OBJECTIVES

Local anesthetic injection into the interspace between the popliteal artery and the posterior capsule of the knee (IPACK) has the potential to provide motor-sparing analgesia to the posterior knee after total knee arthroplasty. The primary objective of this cadaveric study was to evaluate injectate spread to relevant anatomic structures with IPACK injection.

METHODS

After receipt of Institutional Review Board Biospecimen Subcommittee approval, IPACK injection was performed on fresh-frozen cadavers. The popliteal fossa in each specimen was dissected and examined for injectate spread.

RESULTS

Ten fresh-frozen cadaver knees were included in the study. Injectate was observed to spread in the popliteal fossa at a mean ± SD of 6.1 ± 0.7 cm in the medial-lateral dimension and 10.1 ± 3.2 cm in the proximal-distal dimension. No injectate was noted to be in contact with the proximal segment of the sciatic nerve, but 3 specimens showed injectate spread to the tibial nerve. In 3 specimens, the injectate showed possible contact with the common peroneal nerve. The middle genicular artery was consistently surrounded by injectate.

CONCLUSIONS

This cadaver study of IPACK injection demonstrated spread throughout the popliteal fossa without proximal sciatic involvement. However, the potential for injectate to spread to the tibial or common peroneal nerve was demonstrated. Consistent surrounding of the middle genicular artery with injectate suggests a potential mechanism of analgesia for the IPACK block, due to the predictable relationship between articular sensory nerves and this artery. Further study is needed to determine the ideal site of IPACK injection.

Nanoscale Bupivacaine Formulations To Enhance the Duration and Safety of Intravenous Regional Anesthesia

Intravenous regional anesthesia (IVRA; Bier block) is commonly used to anesthetize an extremity for surgery. Limitations of the procedure include pain from the required tourniquet, the toxicity that can occur from systemic release of local anesthetics, and the lack of postoperative pain relief. We hypothesized that the nanoencapsulation of the local anesthetic would prolong local anesthesia and enhance safety. Here, we developed an ∼15 nm micellar bupivacaine formulation (M-Bup) and tested it in a rat tail vein IVRA model, in which active agents were restricted in the tail by a tourniquet for 15 min. After tourniquet removal, M-Bup provided local anesthesia for 4.5 h, which was two times longer than that from a larger dose of free bupivacaine. Approximately 100 nm liposomal bupivacaine (L-Bup) with the same drug dose as M-Bup did not cause anesthesia. Blood levels of bupivacaine after tourniquet removal were lower in animals receiving M-Bup than L-Bup or free bupivacaine, demonstrating enhanced safety. Tissue reaction to M-Bup was benign.

Erector spinae plane block: A cadaver study to determine its mechanism of action

INTRODUCTION

The erector spinae plane (ESP) block is a novel technique for the treatment of acute and chronic pain. Its mechanism and site of action has not yet been explained properly.

OBJECTIVES

In order to explain the mechanism of action of the ESP block, injections were performed with methylene blue to simulate the local anaesthetics and to determine its distribution from the anterior side of the thorax. To find an aperture or channel through which the local anaesthetic passes from posterior to anterior through the muscular and bone structures.

MATERIALS AND METHODS

Four spinal columns of fresh cryopreserved corpses were used. A total of 9 ultrasound-guided ESP blocks were performed in different regions of the specimens using 20ml of 0.01% methylene blue per block. The distribution of the dye was observed from the anterior side of the thorax, measuring the amount of intercostal spaces stained, before and after the removal of the parietal pleura, and the structures in which the stain was found were recorded.

RESULTS

In all blocks of the ESP, dye was found in the paravertebral space, intercostal spaces, and in some cases in the prevertebral chain. The blocks had a mean of 4.6 intercostal spaces stained, with a maximum of 7 and a minimum of 3. The intensity of the dye was greater on the side of the injection, dorsal to the column, than that found in the ventral part below of the pleura. It was not possible to verify a clear channel through which the dye diffuses towards the previous zone.

CONCLUSIONS

From the data collected in this study, it can be deduced that the blockade of the ESP has a mechanism of anaesthetic action similar to paravertebral blocks. The site from which the anaesthetic would cross from the posterior plane of the spine to the anterior region of the thorax was not clear, and should be investigated in future works.

Local Anesthetic Systemic Toxicity

Local anesthetics are commonly used in the perioperative environment to facilitate surgical procedures or to provide postoperative pain management for patients. The use of local anesthetics, however, introduces the risk of complications resulting from local anesthetic systemic toxicity and the risks of increased morbidity and mortality for the surgical patient. Systemic toxicity from the injection or overdose of local anesthetics is a rare but potentially fatal complication that occurs in less than 1 in 1,000 patients. This article provides the perioperative nurse with information about local anesthetics, the signs and symptoms of local anesthetic systemic toxicity, and the information needed to manage a patient experiencing this complication.

Efficacy and pharmacokinetics of bupivacaine with epinephrine or dexmedetomidine after intraperitoneal administration in cats undergoing ovariohysterectomy

The aim of this study was to determine the efficacy and pharmacokinetics of bupivacaine in combination with epinephrine or dexmedetomidine after intraperitoneal administration in cats undergoing ovariohysterectomy. Sixteen healthy adult cats (3.3 ± 0.6 kg) were included in a prospective, randomized, masked clinical trial after obtaining owners' consent. Anesthetic protocol included buprenorphine-propofol-isoflurane. Meloxicam [0.2 mg/kg body weight (BW)] was administered subcutaneously before surgery. Cats were randomly divided into 2 groups to receive 1 of 2 treatments. Intraperitoneal bupivacaine 0.25% (2 mg/kg BW) was administered with epinephrine (BE group; 2 μg/kg BW) or dexmedetomidine (BD group; 1 μg/kg BW) before ovariohysterectomy (n = 8/group). A catheter was placed in the jugular vein for blood sampling. Blood samples were collected for up to 8 h after bupivacaine was administered. Plasma concentrations and pharmacokinetics of bupivacaine were determined using liquid chromatography tandem mass spectrometry (LC-MS/MS) and non-compartmental model, respectively. Pain was evaluated using the UNESP-Botucatu multidimensional composite pain scale (MCPS), the Glasgow composite feline pain scale (GPS), and a dynamic visual analog scale up to 8 h after extubation. Rescue analgesia was provided with buprenorphine if MCPS was ≥ 6. Repeated measures linear models were used for analysis of pain and sedation scores (P < 0.05). Maximum bupivacaine plasma concentrations (Cmax) for BE and BD were 1155 ± 168 ng/mL and 1678 ± 364 ng/mL (P = 0.29) at 67 ± 13 min (Tmax) and 123 ± 59 min (P = 0.17), respectively. Pharmacokinetic parameters and pain scores were not different between treatments (P > 0.05). One cat in the BE group received rescue analgesia (P = 0.30). Intraperitoneal bupivacaine with epinephrine or dexmedetomidine produced concentrations below toxic levels and similar analgesic effects. It is therefore safe to administer these drug combinations in cats undergoing ovariohysterectomy.

Hollow Silica Nanoparticles Penetrate the Peripheral Nerve and Enhance the Nerve Blockade from Tetrodotoxin

The efficacy of tetrodotoxin (TTX), a very potent local anesthetic, is limited by its poor penetration through barriers to axonal surfaces. To address this issue, we encapsulated TTX in hollow silica nanoparticles (TTX-HSN) and injected them at the sciatic nerve in rats. TTX-HSN achieved an increased frequency of successful blocks, prolonged the duration of the block, and decreased the toxicity compared to free TTX. In animals injected with fluorescently labeled HSN, the imaging of frozen sections of nerve demonstrated that HSN could penetrate into nerve and that the penetrating ability of silica nanoparticles was highly size-dependent. These results demonstrated that HSN could deliver TTX into the nerve, enhancing efficacy while improving safety.

Ultrasound-guided genicular nerve block for pain control after total knee replacement: Preliminary case series and technical note

INTRODUCTION

Total knee arthroplasty (TKA) is an operation with moderate to severe postoperative pain. The Fast-Track models employ local infiltration techniques with anaesthetics at high volumes (100-150ml). We proposed a genicular nerve block with low volume of local anaesthetic. The aim of our study is to evaluate the periarticular distribution of these blocks in a fresh cadaver model and to describe the technique in a preliminary group of patients submitted to TKA.

MATERIALS AND METHODS

In the anatomical phase, 4 genicular nerves (superior medial, superior lateral, inferior medial and inferior lateral) were blocked with 4ml of local anaesthetic with iodinated contrast and methylene blue in each (16ml in total). It was performed on a fresh cadaver and the distribution of the injected medium was evaluated by means of a CT-scan and coronal anatomical sections on both knees. The clinical phase included 12 patients scheduled for TKA. Ultrasound-guided block of the 4 genicular nerves was performed preoperatively and their clinical efficacy evaluated by assessing pain after the reversal of the spinal block and at 12h after the block. Pain was measured using the numerical scale and the need for rescue analgesia was evaluated.

RESULTS

A wide periarticular distribution of contrast was observed by CT-scan, which was later evaluated in the coronal sections. The distribution followed the joint capsule without entering the joint, both in the femur and in the tibia. The pain after the reversal of the subarachnoid block was 2±1, requiring rescue analgesia in 42% of the patients. At 12h, the pain according to the numerical scale was 4±1, 33% required rescue analgesia.

CONCLUSION

The administration of 4ml of local anaesthetic at the level of the 4 genicular nerves of the knee produces a wide periarticular distribution. Our preliminary data in a series of 12 patients undergoing TKA seems to be clinically effective. Nevertheless, extensive case series and comparative studies with local infiltration techniques with anaesthetics are needed to support these encouraging results.

Enhanced Triggering of Local Anesthetic Particles by Photosensitization and Photothermal Effect Using a Common Wavelength

On-demand pain relief systems would be very helpful additions to the armamentarium of pain management. Near-infrared triggered drug delivery systems have demonstrated the potential to provide such care. However, challenges remain in making such systems as stimulus-sensitive as possible, to enhance depth of tissue penetration, repeatability of triggering, and safety. Here we developed liposomes containing the local anesthetic tetrodotoxin and also containing a photosensitizer and gold nanorods that were excitable at the same near-infrared wavelength. The combination of triggering mechanisms enhanced the photosensitivity and repeatability of the system in vitro when compared with liposomes with a single photoresponsive component. In vivo, on-demand local anesthesia could be induced with a low irradiance and short irradiation duration, and liposomes containing both photosensitizer and gold nanorods were more effective than those containing just one photoresponsive component. Tissue reaction was benign.

Isobolographic analysis of the cutaneous antinociceptive interaction between bupivacaine co-injected with serotonin in rats

BACKGROUND

The aim of this experiment was to investigate a long-lasting local anesthetic bupivacaine combined with serotonin at inducing cutaneous antinociception.

METHODS

The skin antinociception, characterized by an inhibition of the cutaneous trunci muscle reflex (CTMR) following the pinprick on the dorsal skin of rats, was evaluated. The cutaneous antinociceptive effects of bupivacaine alone, serotonin alone, or bupivacaine co-injected with serotonin in a dose-dependent fashion were constructed, while the drug-drug interactions were evaluated by isobologram.

RESULTS

Subcutaneous serotonin, as well as the local anesthetic bupivacaine provoked dose-related cutaneous antinociception. On an equipotent basis (50% effective dose [ED₅₀]), the relative potency was bupivacaine (0.43 [0.37-0.50] μmol)>serotonin (1.27 [1.15-1.40] μmol) (p<0.01). At the equi-anesthetic doses (ED₇₅, ED₅₀ and ED₂₅), the duration of bupivacaine was similar to that of serotonin at producing cutaneous antinociceptive effects. Co-administration of bupivacaine and serotonin displayed a synergistic antinociception.

CONCLUSIONS

The preclinical data demonstrated that serotonin is less potent in eliciting cutaneous antinociceptive effects but has the similar duration of action, compared with bupivacaine. We also found a more significant depth of the sensory block with bupivacaine+serotonin than bupivacaine alone.

Posture Influences the Extent of Spread of Contrast Medium During Thoracic Epidurography: A Prospective Randomized Trial

BACKGROUND

Various factors influencing the distribution of sensory blockade in epidural anesthesia have been identified; however, reports on the effects of gravity and different postures in thoracic epidural anesthesia have been rare. Medications may be injected with the lateral decubitus or the neutral position; however, it is unclear whether the distribution range of medication is similar or significantly different between these 2 postures.

OBJECTIVE

We focused on identifying the effect of different postures on the distribution of local anesthetics using epidurography at the thoracic level.

STUDY DESIGN

Prospective randomized trial.

SETTING

An interventional pain management practice in South Korea.

METHODS

A total of 68 patients were randomized to either the L group (n = 34, lateral decubitus with neck and hip flexion) or the P group (n = 34, prone position). After completing the insertion of the epidural catheter, the location of the catheter tip was adjusted between T7 and T8 and the patients were asked to change their posture according to their allocated group. Three mL of contrast medium was injected and the total number of segments, including the most cranial and caudal ends of the vertebra, was identified.

RESULTS

The total number of vertebral segments confirmed by contrast medium spread was 7.4 ± 2.2 in group P and 9.2 ± 1.8 in group L. The total number and the number of vertebral segments covered in the caudad direction were higher in group L compared to group P and this was statistically significant (P < 0.001).

LIMITATIONS

We made every effort to make the posture of group L like crouchback, we think that slight differences would present in the flexion angles of the neck and hip among thepatients of group L.

CONCLUSION

Group L demonstrated a more extensive distribution of contrast medium for both the cranial and caudad directions compared to group P.Key words: Epidural, thoracic, contrast medium, injections.

Development of a local anesthetic lidocaine-loaded redox-active injectable gel for postoperative pain management

Although local anesthesia is commonly applied for pain relief, there are several issues such as its short duration of action and low effectiveness at the areas of inflammation due to the acidic pH. The presence of excessive amount of reactive oxygen species (ROS) is known to induce inflammation and aggravate pain. To resolve these issues, we developed a redox-active injectable gel (RIG) with ROS-scavenging activity. RIG was prepared by mixing polyamine-b-poly(ethylene glycol)-b-polyamine with nitroxide radical moieties as side chains on the polyamine segments (PMNT-b-PEG-b-PMNT) with a polyanion, which formed a flower-type micelle via electrostatic complexation. Lidocaine could be stably incorporated in its core. When the temperature of the solution was increased to 37°C, the PIC-type flower micelle transformed to gel. The continuous release of lidocaine from the gel was observed for more than three days, without remarkable initial burst, which is probably owing to the stable entrapment of lidocaine in the PIC core of the gel. We evaluated the analgesic effect of RIG in carrageenan-induced arthritis mouse model. Results showed that lidocaine-loaded RIG has stronger and longer analgesic effect when administered in inflamed areas. In contrast, while the use of non-complexed lidocaine did not show analgesic effect one day after its administration. Note that no effect was observed when PIC-type flower micelle without ROS-scavenging ability was used. These findings suggest that local anesthetic-loaded RIG can effectively reduce the number of injection times and limit the side effects associated with the use of anti-inflammatory drugs for postoperative pain management.

STATEMENT OF SIGNIFICANCE

1. We have been working on nanomaterials, which effectively eliminate ROS, avoiding dysfunction of mitochondria in healthy cells. 2. We designed redox injectable gel using polyion complexed flower type micelle, which can eliminates ROS locally. 3. We could prepare local anesthesia-loaded redox injectable gel (lido@RIG). 4. Drug release could be extended by local administration of lido@RIG. 5. Deprotonation of lidocaine improved anesthetic effect because ROS were eliminated locally by RIG. 6. Local inflammation could be also suppressed by lido@RIG.

Pharmacologic Considerations of Anesthetic Agents in Pediatric Patients: A Comprehensive Review

Acute pain in the pediatric population has important differences in terms of biology, intrapopulation variation, and epidemiology. Discussion as to the pharmacologic considerations of anesthetic agents, such as induction agents, neuromuscular blockers, opioids, local anesthetics, and adjuvant agents, is presented in this article. Special considerations and concerns, such as risk for propofol infusion syndrome and adverse potential side effects of anesthesia agents, are discussed. Anesthesiologists managing pediatric patients need to have a firm understanding of physiologic and pharmacologic differences compared with the adult population. Future studies to improve the understanding of pharmacokinetics in the pediatric population are needed.

3D ultrasound estimation of the effective volume for popliteal block at the level of division

Local anaesthetic injection between the tibial and commmon peroneal nerves within connective tissue sheath results in a predictable diffusion and allows for a reduction in the volume needed to achieve a consistent sciatic popliteal block. Using 3D ultrasound volumetric acquisition, we quantified the visible volume in contact with the nerve along a 5cm segment.

METHODS

We included 20 consecutive patients scheduled for bunion surgery. Ultrasound guided popliteal block was performed using a posterior, out of plane approach at the level of división of the sciatic nerve. Thirty ml of mepivacaine 1.5% and levobupivacaine 0.5% were slowly injected while assessing the injection pressure and the diffusion of the local anaesthetic. Volumetric acquisition was performed before and after the block to quantify the the volume of the sciatic nerve and the volume of the surrounding hypoechoic halo contained inside the connective tissue in a 5cm segment.

RESULTS

All blocks were successful within 20min after the injection. The total estimated volume contained inside the common connective tissue sheath was 6.8±2.6cm³. Of this, the volume of the halo sorrounding the nerve was 4.4±1.7cm³ and the volume inside the sciatic nerve was 2.4±1.7cm³.

CONCLUSIONS

The volume of local anaesthetic in close contact with the sciatic nerve can be estimated by volumetric acquisition. Our results suggest that the effective volume of local anaesthetic needed for a successful sciatic popliteal block could be reduced to less than 7ml.

A Randomized, Multicenter, Double-Blind Study of Local Infiltration Analgesia with Liposomal Bupivacaine for Postsurgical Pain Following Total Knee Arthroplasty: Rationale and Design of the Pillar Trial

INTRODUCTION

Liposomal bupivacaine, a prolonged-release formulation of bupivacaine hydrochloride, is indicated for infiltration into the surgical site for postsurgical analgesia. Results from previous total knee arthroplasty (TKA) studies suggest that analgesic efficacy associated with liposomal bupivacaine may be impacted by variability in infiltration technique. The PILLAR study is designed to assess liposomal bupivacaine efficacy in TKA using a standardized infiltration protocol. Materials and Methods/Design: This phase 4, multicenter, randomized, double-blind, controlled, parallel-group study will compare the safety and efficacy of infiltration with liposomal bupivacaine versus standard bupivacaine for postsurgical pain control in adults undergoing primary unilateral TKA. All subjects will receive a standardized pre-surgical analgesic regimen, and will be randomized to receive either liposomal bupivacaine 266 mg/20 mL (admixed with standard bupivacaine 0.5% 20 mL and expanded to a total volume of 120 mL) or bupivacaine 0.5% 20 mL (expanded to a total volume of 120 mL). The study drug will be infiltrated using six syringes (prefilled with 20 mL of study drug solution) to deliver 1-1.5 mL infusions into prespecified periarticular tissues. All subjects will receive standardized postsurgical analgesia and access to rescue medication. The co-primary efficacy endpoints are area under the curve of visual analog scale pain intensity scores from 12-48 hours postsurgery and total postsurgical opioid consumption from 0-48 hours. Secondary efficacy endpoints include other pain assessments, time to first use of rescue medication, discharge readiness, use of skilled nursing facilities, and hospital length of stay. Safety will be evaluated based on adverse events.

DISCUSSION/CONCLUSION

The use of a standardized protocol comparing infiltration of equal volumes of the study drug, designed by experienced investigators to ensure complete coverage of all areas innervating the surgical site while minimizing leakage of study drug, will help define the role of liposomal bupivacaine in the setting of TKA.

Enhanced skin penetration of lidocaine through encapsulation into nanoethosomes and nanostructured lipid carriers: a comparative study

Lipid based nanoparticles have become a major research object in topical drug delivery to enable drugs to pass the stratum corneum and reach the desired skin layer. The present investigation deals with the encapsulation of lidoacine into nanostructured lipid carriers (NLCs) and nanoethosomes for improving its dermal delivery and consequently local anesthetic efficacy. Concurrently these two topical delivery systems were compared. Lidocaine-loaded NLCs and nanoethosomes were characterized by various techniques and used for an in vitro skin penetration study using excised rat skin and Franz diffusion cells. The nanoparticles were tracked in the skin by following the Rhodamine-labled nanocarriers under fluorescent microscopy. Optimized lidocaine-loaded NLCs (size 96 nm, zeta potential -13.7 mV, encapsulation efficiency (EE) % 69.86% and loading capacity (LC) % 10.47%) and nanoethosomes (size 105.4 nm, zeta potential -33.6 mV, EE 40.14% and LC 8.02%) were chosen for a skin drug delivery study. Higher skin drug deposition of NLCs and nanoethosomal formulations compared to lidocaine hydroalcoholic solution represented a better localization of the drug in the skin. NLC formulation showed the lowest entered drug in the receptor phase of Franz diffusion cell in comparison with nanoethosomes and hydroalcoholic solution confirming the highest skin accumulation of drug. Both colloidal systems showed superiority over the drug solution for dermal delivery of lidocaine, however, NLC exhibited more promising characteristics than nanoethosomes regarding drug loading and skin targeted delivery.

Effects of ketamine and lidocaine in combination on the sevoflurane minimum alveolar concentration in alpacas

This study investigated the effects of ketamine and lidocaine in combination on the minimum alveolar concentration of sevoflurane (MACSEVO) in alpacas. Eight healthy, intact male, adult alpacas were studied on 2 separate occasions. Anesthesia was induced with SEVO, and baseline MAC (MACB) determination began 45 min after induction. After MACB determination, alpacas were randomly given either an intravenous (IV) loading dose (LD) and infusion of saline or a loading dose [ketamine = 0.5 mg/kg body weight (BW); lidocaine = 2 mg/kg BW] and an infusion of ketamine (25 μg/kg BW per minute) in combination with lidocaine (50 μg/kg BW per minute), and MACSEVO was re-determined (MACT). Quality of recovery, time-to-extubation, and time-to-standing, were also evaluated. Mean MACB was 1.88% ± 0.13% and 1.89% ± 0.14% for the saline and ketamine + lidocaine groups, respectively. Ketamine and lidocaine administration decreased (P < 0.05) MACB by 57% and mean MACT was 0.83% ± 0.10%. Saline administration did not change MACB. Time to determine MACB and MACT was not significantly different between the treatments. The quality of recovery, time-to-extubation, and time-to-standing, were not different between groups. The infusion of ketamine combined with lidocaine significantly decreased MACSEVO by 57% and did not adversely affect time-to-standing or quality of recovery.

[Classification of local anesthesia methods]

The traditional classification methods of dental local anesthesia must be modified. In this paper we proved that the vascular mechanism is leading component of spongy injection. It is necessary to take into account the high effectiveness and relative safety of spongy anesthesia, as well as versatility, ease of implementation and the growing prevalence in the world. The essence of the proposed modification is to distinguish the methods in diffusive (including surface anesthesia, infiltration and conductive anesthesia) and vascular-diffusive (including intraosseous, intraligamentary, intraseptal and intrapulpal anesthesia). For the last four methods the common term «spongy (intraosseous) anesthesia» may be used.

Local anesthetic injection deep to the fascia iliaca at the level of the inguinal ligament: the pattern of distribution and effects on the obturator nerve

STUDY OBJECTIVE

The femoral, lateral femoral cutaneous, and obturator nerves (ONs) can reportedly be blocked using a single-injection deep to the fascia iliaca (FI) at the level of the inguinal ligament. Two commonly used methods (the FI compartment and 3-in-1 blocks) have produced inconsistent results with respect to local anesthetic distribution and effect on the ON. To date, no study of either method has been performed using advanced imaging techniques to document both needle placement and local anesthetic distribution. We report the outcome of a series of 3-in-1 and FI blocks performed using ultrasound to guide needle position and magnetic resonance imaging (MRI) to define local anesthetic distribution.

DESIGN

Patients were prospectively studied, and images were interpreted using a randomized and blinded protocol.

SETTING

The study was performed in the perioperative area of an academic orthopedic specialty hospital.

PATIENTS

Ten patients (ASA 1-2) having anterior cruciate ligament reconstruction received either 3-in-1 or FI compartment blocks for postoperative analgesia using the surface landmarks described for these techniques.

INTERVENTIONS

Ultrasound was used to position the injecting needle immediately deep to the FI. Local anesthetic distribution was studied using MRI.

MEASUREMENTS

Patients were examined for motor and/or sensory function of the femoral, obturator, and lateral femoral cutaneous nerves. Magnetic resonance imaging was used to document the limits of injectate distribution.

MAIN RESULTS

Magnetic resonance imaging showed distribution of injectate over the surface of the iliacus and psoas muscles to the level of the retroperitoneum. No patient showed medial extension of injectate to the ON. At the level of the inguinal ligament, injectate extended laterally toward the anterior superior iliac spine and medially to the femoral vein. All patients had significant weakness with extension of the knee and sensory loss over the anterior, lateral, and medial thigh. No patient demonstrated decreased hip adductor strength.

CONCLUSIONS

Ultrasound and MRI show consistent superior extension of local anesthetic to the level of the retroperitoneum for both techniques. There was reliable clinical effect on the femoral and lateral femoral cutaneous nerves. However, none of the injections produced evidence of ON block either at the level of the retroperitoneum or the inguinal ligament.

[Preliminary study on transdermal characteristics and sunface anesthetic effects of lidocaine hydrochloride loaded trans-activator of transcription peptide conjugated nano-niosome in animals]

OBJECTIVE

To prepare a new dental topical anesthetics, lidocaine hydrochloride loaded trans-activator of transcription peptide conjugated nano-niosome (LID-TAT-N), and to evaluate its transdermal properties and topical anesthesia effects.

METHODS

LID-TAT-N was prepared using reverse-phase evaporation method, and lidocaine loaded conventional liposome (LID-CL) was prepared in the same manner as positive control. The diameter, ζ potential and encapsulation efficiency of LID-TAT-N and LID-CL were measured. The skin permeation of LID-TAT-N was examined, and compared with LID-CL and lidocaine injection (LID-IJ, as negative control), using a Franz diffusion cell mounted with depilated mouse skin in vitro for 12 hours. Each experiment was repeated six times. The anesthetic effect of the new topical anesthetic was investigated on the cornea of rabbits.

RESULTS

The mean diameter of LID-TAT-N was smaller than that of LID-CL [(152.7 ± 10.6) nm vs. (259.5 ± 15.5) nm, P < 0.01]. The 12 h cumulative permeation amount was significantly higher in LID-TAT-N group [(1 340.0 ± 97.5) µg · cm(-2)] than those of LID-CL and LID-IJ groups [(1 060.6 ± 80.2), (282.6 ± 65.1) µg · cm(-2), respectively, P < 0.05]. Rabbit corneal reflex results showed that LID-TAT-N had anesthetic effect and the duration of analgesia [(24.8 ± 2.8) min] was also longer than that of LID-IJ [(14.5 ± 2.3) min, P < 0.05].

CONCLUSIONS

LID-TAT-N had good transdermal ability, and the advanced skin penetration feature can improve its tropical anesthetic effect.

Influence of Desorption Conditions on Analyte Sensitivity and Internal Energy in Discrete Tissue or Whole Body Imaging by IR-MALDESI

Analyte signal in a laser desorption/postionization scheme such as infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) is strongly coupled to the degree of overlap between the desorbed plume of neutral material from a sample and an orthogonal electrospray. In this work, we systematically examine the effect of desorption conditions on IR-MALDESI response to pharmaceutical drugs and endogenous lipids in biological tissue using a design of experiments approach. Optimized desorption conditions have then been used to conduct an untargeted lipidomic analysis of whole body sagittal sections of neonate mouse. IR-MALDESI response to a wide range of lipid classes has been demonstrated, with enhanced lipid coverage received by varying the laser wavelength used for mass spectrometry imaging (MSI). Targeted MS(2) imaging (MS(2)I) of an analyte, cocaine, deposited beneath whole body sections allowed determination of tissue-specific ion response factors, and CID fragments of cocaine were monitored to comment on wavelength-dependent internal energy deposition based on the "survival yield" method.

Dilution Effect of Intra-articular Injection Administered After Knee Arthroscopy

The hypothesis was that agents delivered intra-articularly after knee arthroscopy will be diluted by residual arthroscopic fluid. Diagnostic arthroscopy was performed on six cadaver knees. Each procedure was followed by an intra-articular injection of a dye solution. Intra-articular aspirates were gathered from three locations. With significance set at p < .05, the aspirates were compared with the initial dye concentration and with each other. No significant difference was noted among the sites, indicating that no specific knee area was exposed to a higher dye concentration. There was a significant difference in dye concentration of the aspirates when compared with the dye's initial concentration. The concentration of fluid injected intra-articularly after arthroscopy was diluted by 27%. These data indicate that agents injected into the knee postarthroscopy are significantly diluted. In vitro and in vivo experiments evaluating chondrotoxicity of various anesthetic agents may not accurately reflect the actual concentration of the drug within the knee joint unless dilution effects are taken into account.

[COMPARATIVE EVALUATION OF CURRENT METHODS OF ANESTHESIA IN PERFORMANCE OF TRANSRECTAL PROSTATE BIOPSY]

Prostate biopsy guided by transrectal ultrasonography (TRUS) is largely used in prostate cancer diagnostics. This procedure is usually quite painful and fear of pain could scare patients from this important research. The aim of the study was to compare methods of anesthesia for prostate biopsy. The patients were divided into 4 groups (40 patients in each group). TRUS-guided periprostatic anesthesia with 1% solution of lidocaine (10 ml) was carried out in the first group. An intrarectal introduction of 5 g EMLA cream (lidocaine 2,5% and prilocaine 2,5%) was applied in the second group. The intrarectal introduction of 10% lidocaine spray (3 doses) was used in the third group. Placebo as ultrasonic gel was utilized for the fourth group. The authors used the 100-score linear visual analog scale (LVS 1-100) and 5-score numeric visual scale (NVS-4). Minimal scores of pain were obtained in patients using TRUS-guided periprostatic anesthesia with 1% solution of lidocaine (10 ml). This type of anesthesia didn't lead to increase of the number of complications.

PHARMACOTHERAPY FOR THE ELDERLY DENTAL PATIENT

Current demographic data clearly show that the North American population is aging, and projections suggest that the percentage of older people will increase. The elderly often suffer from multiple chronic conditions that affect their quality of life, use of health services, morbidity and mortality. Also, in those of advanced age, the pharmacokinetics and pharmacodynamics of many drugs are altered. Polypharmacy increases the incidence of adverse drug reactions and drug interactions in this population. Thus, the dentist must be continually aware of the pharmacologic status of each patient and consider the likelihood of interactions between drugs prescribed by the dentist, drugs prescribed by the physician and drugs that are self-administered, including over-the-counter medications and natural supplements. In this article, we discuss pharmacokinetic and pharmacodynamic changes in the elderly patient, polypharmacy and the changes in prescribing for our dental patients. Specific emphasis is placed on the drugs commonly prescribed by dentists: local anesthetics, analgesics and antibiotics.

Rationalization of reduced penetration of drugs through ceramide gel phase membrane

Since computing resources have advanced enough to allow routine molecular simulation studies of drug molecules interacting with biologically relevant membranes, a considerable amount of work has been carried out with fluid phospholipid systems. However, there is very little work in the literature on drug interactions with gel phase lipids. This poses a significant limitation for understanding permeation through the stratum corneum where the primary pathway is expected to be through a highly ordered lipid matrix. To address this point, we analyzed the interactions of p-aminobenzoic acid (PABA) and its ethyl (benzocaine) and butyl (butamben) esters with two membrane bilayers, which differ in their fluidity at ambient conditions. We considered a dioleoylphosphatidylcholine (DOPC) bilayer in a fluid state and a ceramide 2 (CER2, ceramide NS) bilayer in a gel phase. We carried out unbiased (100 ns long) and biased z-constraint molecular dynamics simulations and calculated the free energy profiles of all molecules along the bilayer normal. The free energy profiles converged significantly slower for the gel phase. While the compounds have comparable affinities for both membranes, they exhibit penetration barriers almost 3 times higher in the gel phase CER2 bilayer. This elevated barrier and slower diffusion in the CER2 bilayer, which are caused by the high ordering of CER2 lipid chains, explain the low permeability of the gel phase membranes. We also compared the free energy profiles from MD simulations with those obtained from COSMOmic. This method provided the same trends in behavior for the guest molecules in both bilayers; however, the penetration barriers calculated by COSMOmic did not differ between membranes. In conclusion, we show how membrane fluid properties affect the interaction of drug-like molecules with membranes.

Ultrasound visibility of spinal structures and local anesthetic spread in children undergoing caudal block

This study assessed ultrasound visibility of spinal structures in children and observed the extent of local anesthetic spread within the epidural space during caudal block. Spinal structures were evaluated with ultrasound from the sacral area to the thoracic area in 80 children, and drug spread levels were observed after caudal injection of 0.5, 1.0, 1.25 and 1.5 mL/kg local anesthetic. The conus medullaris, dural sac and dura mater were easily identified with ultrasound in most children. However, ligamentum flavum visibility declined with increasing vertebral level and markedly decreased at the thoracic level in children older than 7 mo or heavier than 8.5 kg. Drug spread was higher with increasing volume (p < 0.001) and in children ≤12 mo more than children >12 mo (p < 0.001); drug spread was significantly correlated with age (R(2) = 0.534). Spread levels assessed with ultrasound were roughly two to three segments lower than those in previous radiologic studies.

The use of skin needling for the delivery of a eutectic mixture of local anesthetics

AIM

The use of skin needling is believed to aid the transdermal delivery of drugs, even if it is mostly used for skin collagen induction. The aim of this paper was to use skin needling, combined with a local anesthetic EMLA (eutectic mixture of lidocaine and prilocaine), as a way to enhance transdermal drug penetration and optimize the analgesic effects of common local anesthesia.

METHODS

We recruited 15 patients. For each patient of our study we defined a skin area of 3 cm2 from two forearms: on one side, we used skin needling first and immediately thereafter applied the EMLA in occlusion for 60 minutes; on the other one, we only applied EMLA in occlusion for 60 minutes. Then, pain was induced in each patient's forearm by introducing a 27 G needle into the skin 4 mm deep three times. Lastly, pain sensation measures were registered and a middle value was calculated.

RESULTS

When skin needling is used in conjunction with EMLA applied in occlusion for 60 minutes on skin forearms, the level of pain sensation registered was significantly reduced on a Visual Analogue Scale compared to the application of EMLA alone.

CONCLUSION

The use of skin needling can improve the transdermal delivery of an emulsion-like eutectic mixture of local anesthetics (EMLA) and can introduce the use of this method for delivering topical molecules in dermatology.

Plasma concentrations of bupivacaine after spinal anesthesia with single shot femoral nerve block and periarticular injection in total knee arthroplasty

OBJECTIVE

To determine the plasma concentrations of bupivacaine and toxicity after periarticular injection (PAI) combined with spinal anesthesia and femoral nerve block (FNB).

MATERIAL AND METHOD

Forty-three patients scheduled for unilateral total knee arthroplasty (TKA) were enrolled in the prospective observational study. The dose of bupivacaine for spinal anesthesia was adjusted by the attending anesthesiologist. The single-shot femoral nerve block (FNB) and periarticular injection (PAI) were performed with 20 ml of 0.5% bupivacaine and 20 ml of 0.25% bupivacaine respectively. Venous blood samples from antecubital vein were collected at 60 minutes after femoral nerve block and at the time before periarticular injection, then at 15, 30, 45, and 60 minutes afterwards. Plasma bupivacaine concentrations were analyzed, using a high performance liquid chromatography with tandem mass spectrometry.

RESULTS

Ten males and 32 females, ASA I-II were included. The highest median plasma concentration was 586.22 ng/ml (min = 245.39, max = 1,614.36) at 45 minutes after periarticular injection. The maximum plasma bupivacaine concentration was 1,709.71 ng/ml at 60 minutes after periarticular injection. No clinical toxicity was encountered

CONCLUSION

The plasma concentration of bupivacaine in patients performed periarticular injection with 20 ml of 0.25% bupivacaine after spinal anesthesia and single-shot femoral nerve block with 20 ml of 0.5% bupivacaine is below the plasma toxic level.

[Analgesic efficacy and clinical safety of intraperitoneal instillation combined with rectus sheath block using ropivacaine for pain relief after laparoscopic gynecological surgery]

BACKGROUND

The aim of this study was to evaluate the analgesic efficacy and safety of rectus sheath block combined with intraperitoneal instillation using two doses of ropivacaine in patients undergoing laparoscopic gynecological surgery.

METHODS

Altogether 53 consenting women were randomized to receive intraperitoneal infiltration with 0.25% ropivacaine or 0.5% ropivacaine followed by rectus sheath block with 0.375% ropivacaine. The outcomes of clinical safety were measured using plasma concentration of local anesthetics and occurrence of toxic symptoms. The analgesic efficacy was assessed using numerical rating scales for pain and morphine consumption up to 24 hours after surgery.

RESULTS

Patients' baseline characteristics, surgical factors, and analgesic outcomes were comparable between the two groups. Although peak plasma concentration of ropivacaine was significantly higher in patients receiving 0.5% ropivacaine, none of analyzed concentrations was above the toxic ones. Besides, no patients showed any symptoms of local anesthetic toxicity.

CONCLUSIONS

The present study showed that the combination of rectus sheath block with intraperitoneal instillation of ropivacaine was safe and potent enough to relieve pain after laparoscopic surgery.

Topical anesthetics for cosmetic dermatologic procedures

AIM

The aim of our study is to value the vasoconstrictor effect of two most utilized topical anesthetics, the first one containing a mixture 2.5% lidocaine and 2.5% prilocaine and the second one containing 4% liposomal lidocaine, in the treatment of vascular lesion during cosmetic dermatologic procedures.

METHODS

Ten healthy volunteers were enrolled in our department. They showed telangiectasias, measuring between 0.5 and 1 millimeter in diameter on their face and limbs. Five volunteers were randomized to receive topical 4% liposomal lidocaine and five to receive 2.5% lidocaine and 2.5% prilocaine. In all treated areas, the 4% liposomal lidocaine was left for at least 30 minutes and the 2.5% lidocaine and 2.5% prilocaine was left for at least 60 minutes.

RESULTS

Clinically, the volunteers who received the 4% liposomal lidocaine showed minimal vasoconstrictor difference between before and after treatment; while the others who received the 2.5% lidocaine and 2.5% prilocaine showed a major vasoconstrictor effect. Furthermore the 4% liposomal lidocaine cream has the advantage of an anesthetic effect after 30 minutes, rather than 60 minutes for the 2.5% lidocaine and 2.5% prilocaine cream.

CONCLUSION

This study demonstrated that the 4% liposomal lidocaine has relatively minor vasoconstrictor effect when compared to the other anesthetic, and it shows how this type of anesthetic allows a clear vision of the lesion during the dermatologic procedures. Furthermore, this cream achieves an anesthetic effect in 30 minutes rather than the 60 minutes required for the other cream, making the first one more suitable for cosmetic dermatologic procedures and for the emergency.

Topical lidocaine enhanced by laser pretreatment: a safe and effective method of analgesia for facial rejuvenation

BACKGROUND

Injectable forms of anesthesia for nonsurgical facial rejuvenation, although efficacious, are uncomfortable for the patient. Preclinical studies have demonstrated that laser pretreatment at low energies enhances absorption of topical lidocaine.

OBJECTIVES

The authors assess the safety and efficacy of laser-assisted transdermal delivery of topical anesthetic.

METHOD

Ten patients were split into 2 groups (A and B). All patients received 15 g of BLT (20% benzocaine, 6% lidocaine, and 4% tetracaine triple anesthetic cream) for 20 minutes with no occlusion. Then the cream was removed and the first blood draw taken. Group A patients were pretreated with the full ablative laser and group B patients with a fractional ablative laser to the full face. A further 15 g BLT was applied for another 20 minutes. Group A patients then underwent full ablative laser treatment, and group B received fractionated ablative laser treatment. Blood draws were taken at 60, 90, 120, 180, and 240 minutes after the initial topical anesthetic application, and the serum was analyzed for lidocaine and monoethylglycinexylidide (MEGX) levels. Patients were asked to rate the pain felt at intervals during the procedure.

RESULTS

No patient required supplemental nerve blocks. Pain scores were equivalent at the end of the first pass for both groups (P = .436). Group A patients had significantly lower pain scores at the start of the second laser treatment (P = .045), but pain scores became equivalent by the end (P = .323). Combined serum lidocaine and MEGX levels were significantly higher in group A patients up to 90 minutes (peak average of 0.61 µg/mL for group A and 0.533 µg/mL for group B; P = .0253), which corresponded to greater initial analgesic effect.

CONCLUSIONS

Data from this study demonstrate that topical anesthetic for facial rejuvenation can be enhanced with laser pretreatment while maintaining safe blood serum levels. Further studies should examine optimal application amount and time to allow safe multipass facial rejuvenation without the need for invasive nerve blocks.

[Effect of liver cirrhosis on pharmacokinetics and pharmacodynamics of drugs]

Metabolic liver functions are significantly involved in the total clearance of a number of drugs. In liver cirrhosis the reduced drug elimination is a result of the blood flow through the liver, hepatocytes function and volume of hepatic tissue. Pharmacokinetic and pharmacodynamic changes depend on the nature and degree of hepatic impairment and on the characteristics of the dosed drug. Hepatocytes have a different extraction ability with respect to the individual drugs. The following are examples of drugs with high hepatic extraction: anodyne, propranolol, metoprolol, verapamil and lidocaine. These drugs are significantly dependent on the first passage through the liver. Intrahepatic and extrahepatic collateral blood flows significantly increase their bio-logical availability and reduce the clearance. The reduction in hepatic clearance of drugs with low extraction coefficient, such as chlordiazepoxide, diazepam or furosemide, is a result of its own limited functional capacity to eliminate the drug. Predicting a hepatic metabolic disorder based on a common bio-chemical assessment of enzyme activities is not sufficient. In advanced liver cirrhosis a higher risk is demonstrated for drugs with a narrow therapeutic width. It is always necessary to take into account whether the pharmacotherapy is necessary, use small doses and cautiously monitor the patient.

Pharmacokinetics of Articaine Hydrochloride in Tumescent Local Anesthesia for Liposuction

The aim of the investigation was to assess the pharmacokinetic characteristics and safety of articaine HCl used in tumescent local anesthesia for liposuction. Maximum plasma concentrations of articaine HCl were observed from 136 to 264 ng/mL, on average, from 1.2 to 4.3 hours after the start of infiltration, depending on the area of liposuction. The average extent of absorption ranged from 827 to 2203 ng*h/mL. Average maximum plasma concentrations of articainic acid ranged from 1719 to 7292 ng/mL. The high articainic acid concentrations at 1 hour after the start of infiltration indicate that articaine HCl was hydrolyzed rapidly by esterases in tissue and plasma. Although up to 38.2 mg/kg body weight articaine HCl was applied, no cardiac side effects or symptoms of central nervous intoxication occurred. Articaine HCl provided a safe and sufficient analgesia for tumescent liposuction.

Tumescent anaesthesia

Tumescent anaesthesia describes the practice of injecting a very dilute solution of local anaesthetic combined with epinephrine and sodium bicarbonate into tissue until it becomes firm and tense (tumescent). It was initially described in the field of liposuction but now surgical applications for the technique are widely varied ranging across vascular surgery, breast surgery, plastic surgery and ENT procedures. It is widely used in both hospital- and office-based environments and may form the sole method of anaesthesia for surgery. Advantages include a reduction in blood loss through both epinephrine-induced vasoconstriction as well as hydrostatic compression from the tumescent effect. Sodium bicarbonate reduces pain associated with the injection of an acidic local anaesthetic solution. Due to the unique pharmacokinetic profile of this technique lidocaine doses of 35 mg/kg bodyweight have been shown to be safe for liposuction procedures. Tumescent lidocaine is absorbed very slowly from subcutaneous tissues producing lower, and more delayed, peak blood levels compared to other routes, as well as extended postoperative analgesia. Slow systemic absorption allows the rapid hepatic plasma clearance of lidocaine to maintain safe local anaesthetic blood levels. This slow absorption from subcutaneous tissue has been likened to a depot injection. Careful attention must be given to appropriate local anaesthetic dosage alterations in cases of co-administration with agents affecting hepatic drug clearance or conditions reducing liver blood supply. Adherence to these pharmacological principles has produced an exemplary safety record for this technique to date.

Influence of carbon dioxide insufflation of the neck on intraocular pressure during robot-assisted endoscopic thyroidectomy: a comparison with open thyroidectomy

BACKGROUND

Increased intraocular pressure (IOP) during surgery can result in serious ophthalmic complications. We hypothesized that carbon dioxide (CO₂) insufflation of the neck during endoscopic thyroidectomy would constrict the jugular veins mechanically, causing elevated venous pressure and thus elevated IOP. We compared IOP changes at each step of open thyroidectomy (OT) versus robot-assisted endoscopic thyroidectomy (RET) METHODS: Perioperatively, IOP was measured at six time points in patients undergoing OT (n = 18) or RET with CO₂ insufflation (n = 19). Anesthesia, ventilatory strategy, intravenous infusions, and surgical positioning were standardized

RESULTS

In both groups, induction of anesthesia reduced IOP, but surgical positioning with the neck in extension had no effect on IOP. In the OT group, IOP remained unchanged during anesthesia. In the RET group, CO₂ insufflation significantly increased IOP to an average of 3.6 ± 3.0 mmHg higher than the previous measurement (P < 0.001), and this IOP increase persisted immediately before gas deflation. These elevated IOP values during CO₂ insufflation in the RET group were significantly higher than those at corresponding time points in the OT group. However, these elevated IOP values were similar to the pre-anesthetic baseline IOP CONCLUSION: CO₂ insufflation of the neck at pressure of 6 mmHg increased the IOP significantly compared with open thyroidectomy. However, this increase in IOP could be balanced by an anesthetic-induced IOP-lowering effect, thereby having no clinical significance in patients with normal IOP undergoing robot-assisted endoscopic thyroidectomy.

In vitro and in vivo entrapment of bupivacaine by lipid dispersions

Intravenous lipid emulsion is recommended as treatment for local anesthetic intoxication based on the hypothesis that the lipophilic drug is entrapped by the lipid phase created in plasma. We compared a 15.6 mM 80/20 mol% phosphatidyl choline (PC)/phosphatidyl glycerol (PG)-based liposome dispersion with the commercially available Intralipid® emulsion in a pig model of local anesthetic intoxication. Bupivacaine-lipid interactions were studied by electrokinetic capillary chromatography. Multilamellar vesicles were used in the first in vivo experiment series. This series was interrupted when the liposome dispersion was discovered to cause cardiovascular collapse. The toxicity was decreased by an optimized sonication of the 50% diluted liposome dispersion (7.8 mM). Twenty anesthetized pigs were then infused with either sonicated PC/PG liposome dispersion or Intralipid®, following infusion of a toxic dose of bupivacaine which decreased the mean arterial pressure by 50% from baseline. Bupivacaine concentrations were quantified in blood samples using liquid chromatography/mass spectrometry. No significant difference in the context-sensitive plasma half-life of bupivacaine was detected (p=0.932). After 30 min of lipid infusion, the bupivacaine concentration was 8.2±1.5 mg/L in the PC/PG group and 7.8±1.8 mg/L in the Intralipid® group, with no difference between groups (p=0.591). No difference in hemodynamic recovery was detected between groups (p > 0.05).

[Studies of local anaesthetics - part 197. Effect of xylitol on pharmaceutical availability of lidocaine and flow properties of hydrogels]

The paper examines the formulation of hydrogel on the base of a synthetic polymer containing a local anaesthetic and a mass-produced drug in the form of a solution with an antiphlogistic effect. It aimed to prepare a hydrogel of a suitable composition with suitable flow properties and drug release, the active ingredient being lidocaine hydrochloride. Besides the role of a synthetic polymer which ensures that the active ingredient remains at the affected site, an important role in the formulation is played by the presence of an artificial sweetener, which to a great extent as a taste correcting agent of the unpleasant taste of the active ingredient influences the compliance of many patients. The study examined the effect of concentration of the artificial sweetener xylitol on the liberation of the active ingredient from prepared hydrogels. The optimum concentration of the artificial sweetener was adjusted to a degree which does not affect the qualitative properties of the active ingredient.

KEYWORDS

lidocaine hydrochloride, xylitol, hydrogel, liberation.